Hydrocarbon oil composition



Patented Nov. 13, 1945 HYDROGARBON OIL COMPOSITION No Drawing.Application October 30, 1942, Serial No. 463,944

4: fillaims.

This invention relates to improvements in bydrocarbon oils. Morespecifically it relates to lubricating oils particularly useful asturbine oils and slushing oils, etc, because of their lubricating,anti-corrosion, film-forming and other unique properties.

The lubrication of the bearings, governing mechanism and other parts ofmodern steam turbines is usually accomplished by means of a force-feedsystem which includes the necessary piping, pump, settling tank orcentrifuge, filter, cooler, etc., to circulate the oil and to collectand remove contaminating materials. In such systems the oil is subjectedto continuous changes in temperature in its flow from the hearings tothe cooler. It also is generally contaminated with water from leakage ofsteam into the system and under these conditions of temperature,moisture, and exposure to air is liable to deteriorate with theformation of acidic oxidation products. This is particularly true in thecase of the highly refined oils and white oils commonly employed inturbine lubrication. Ihe acidic oxidation products, water, air, etc., inthe system contact the metal surfaces corroding them and resulting inthe formation of metal salts and X- ides which increase the tendency ofthe oil to form stable emulsions with the water therein.

Since the effective life of a turbine oil is ended when it tends to formemulsions of excessive stabillty, it will be seen that prevention ofoxidation of the oil and corrosion of the metal surfaces of the turbineis an essential requirement.

Although every effort is made to prevent the entrance of water into thecirculating system and efforts are made to remove it as fast as itenters some water will ordinarily be present in the turbine oil at alltimes. Since metal surfaces are preferentially wet with water ratherthan oil even small amounts of water will collect on the metal surfacesand corrode these parts with the formation of undesirable salts andoxides.

One of the objects of the present invention is, therefore, to provide anoil which prevents preferential wetting of metal surfaces with water.Another object is the prevention of corrosion of metal parts by thecombined action of air and moisture. Another object of the invention isto reduce the tendency of the oil to oxidize with the formation ofacidic products. Still another object of the invention is to provideturbine oils with decreased tendency to form stable oil-water emulsions.A still further object of the invention is to provide a lubricating oilwhich accomplishes the aforesaid objects and retainsthese advantageseven after extended use. These objects and others which will be apparentand from what is said hereinafter are accomplished by us by providing alubricating oil containing an alkyl amine and an alkyl phenol of thekind and in the proportions hereinafter set forth.

Although the use of certain amines in lubricating oil has been proposedto reduce corrosion most of the amines which. have been suggested areunsuitable in turbine oils. As pointed out herelnabove the water leakinginto the turbine lubricating system is ordinarily. collected andremoved. Most of the amines suggested for use in lubricating oilheretofore have been water-soluble and obviously when used in turbineoils are extracted from the oil by the water and are removed from thesystem with it. The higher alkyl amines sucn as those having 16 to 18carbon atoms in the alkyl groups are extremely waterlnsoluble but arealso difllcultly oil-soluble. Although these higher amines may bedissolved in a refined oil by heating this property of oil-insolubilityhas discouraged their use since they come out of the oil when it iscooled down to room temperature and in the cooling system of a turbinecirculation system.

We have discovered, however, that when primary alkyl amines containing16 to 18 carbon atoms in the alkyl group are mixed with alkyl phenolsthe two apparently react forming an addition salt which is highlysoluble in the lubricating oil. This enables us to dissolve the higheralkyl amines in lubricating oils with a minimum of effort and after thecomposition is dissolved in the oil it remains soluble therein eventhough the oil is cooled below freezing. For example, a 2.5% solution ofoctadecyl amine in a highly refined Pennsylvania oil SAE grade No. 20prepared by heating and stirring octadecyl amine with the oil untilfully dissolved became cloudy from the precipitation of the amine whencooled to room temperature. On the other hand a sample of the same oilcontaining 2.5% by weight of octadecyl amine and 2.5% by weight of2,4-diamyl phenol remained perfectly clear even though cooled to as lowas 6 C.

Despite the fact that the alkyl amines and the alkyl phenol form anoil-soluble salt we have discovered that the salt is more effective inpreventing corrosion, oxidation, and promoting film-formation thaneither of the two components alone. This surprising discovery enables usto provide lubricating oils particularly useful n. the lu rication ofsteam turbines having all the advantageous characteristics hereinbeforeset forth.

The alkyl amine-alkyl phenol salt in our improved hydrocarbon oilcomposition is heteropolar in character and the polar portion of themolecule attaches itself readily to metal surfaces. The non-polarportion of the molecule is hydrophobic and tends to repel water andattract hydrocarbon oil. This action results in the formation of a thinfilm of oil on the metal surface. For example, when a polished steelspecimen covered with drops of water was immersed in oil containingsmall percentage of the alkyl amine-alkyl phenol salt it was found thatthe waterwas replaced by a thin film of oil.

The alkyl amine-alkyl phenol salt being also highly water-insoluble isnot washed away from the metal. surface by the action ofwater in theoil. The weakly alkaline nature of the salt also helps it to reducecorrosion. The salt also shows the anti-oxidant effects characteristicof phenols and thus tends to inhibit the oxidation of the oilcirculating in the system. It will be seen, therefore, that thiscombination of characteristics is highly advantageous in lubricatingoils for use in steam turbines. V

The effectiveness of our new lubricating oil composition may beillustrated by means of the following test in which thecorrosion-inhibiting eflects of the composition are clearly shown. Thistest was as follows: a 400 ml. tall-form beaker containing 200 g. of thelubricant to be tested was mounted on a steam bath, a stainless steelstirrer was placed so that the blades were /2" from the bottom ofthe'beaker. A highly polished cold rolled steel specimen, 4.5" long andhaving a diameter of 1 s" was immersed in the lubricant to a depth ofapproximately 2". After stirring the lubricant for 10 minutes 4 ml. (2%)of water was added and the stirring continued. The specimen was examined/2 hour after the addition of water for the formation oi" brown rustspots and pitting. The temperature of the oil was then raised to 50 C.and the test continued. Periodic examinations were made at /2 hourintervals.

The results shown in the following table were obtained by comparing twolubricating 011 samples one of which contained 0.1% of a mixture ofequal parts byweight of octadecyl amine and 2,4-diamyl phenol dissolvedin a highly refined Pennsylvania oil SAE-20. The other sample containingno additive was used as a control.

The alkyl amines which we employ are as stated above, primary alkylamines containing 16 to 18 .carbon atoms, inclusive, in the alkyl chain.Al-

though we may use substantially pure amines we ordinarily; for reasonsof economy, emp y th commercial grades of octadecyl amine, arepresentative sample of which contained 25% octadecyl amine, 25%hexadecyl amine and 50% octadecenyl amine. It was a light-coloredwax-like solid having a melting point of about 45 0., a boiling point of300 to 360 0., difllouitly soluble in rhydrocarbon oils and totallyinsoluble in water.

Other alkyl amines of this character having 16 to 18 carbon atoms andwhich are insoluble in water and diflicultly soluble in lubricating oilsare also included within the'purview of our invention and may beemployed by -us. Such mixed alkyl amines are indirectly obtained fromthe fatty acids of animal and vegetable fats and oils and contain bothsaturated and unsaturated alkyl groups and minor amounts of shorterchain alkyl amines.

The alkyl phenols which we employ are oilsoluble mono-, diand tri-alkylphenols such as. for example, octyl phenol, decyl phenol, ethylhexylphenol, dodecyl phenol, di-amyl phenol, di-octyl phenol, di-ethylhexylphenol, di-dodecyl phenol, 2,4,6-tritertiary butyl phenol and otheroil-soluble straight or branched chain alkyl phenols. We prefer thosealkyl phenols having a total of at least 5 carbon atoms in the alkylchains because of their greater oil solubility.

Ordinarily the alkyl amine and alkyl phenol are employed by us insubstantially equal molecular proportions. As commercially availablealkyl amines of the type employed by us vary considerably in purity, theamounts thereof employed in proportion to the alkyl phenol will varysomewhat and it is desirable to use a slight excess of the amine overthe theoretical quantity required to form a salt with the alkyl phenolemployed. An excess of either component. will do no harm, however.

' The amount of alkyl amine-alkyl phenol salt necessary to giveeffective results in our new hydrocarbon oil composition is very smallranging from aslow as 0.02% to 5.0% by weight based on the total weightof the oilin the composition. The phenol-amine corrosion inhibitor maybe used in conjunction with other additives of turbine 'oils such asantioxidants or oxidation inhibitors if desired.

' Although we have described our invention with particular reference tothe improvement of turbine oils, it will be understood that it alsocontemplates the improvement of other hydrocarbon oils intended forother purposes where a film- .forming anti-corrosion oil is desirable.As will be seen from the foregoing the alkyl phenol,- higher alkyl'amine salts attach themselves to metal surfaces forming water insolublefilms not easily washed away by water. The film is compatible with oil,however, and results in the metal surface being covered with a thin filmof tenaciously held oil. This effect is of particular value inanti-corrosion oils of the slushing 011 type and the improvement ofthese oils is considered by us to be a part of the present inventionandembodied in the scope of the appended claims.

We claim:

1. A lubricating oil composition for the lubrication of steam turbinescomprising a major proportion of a hydrocarbon lubricating oil and from0.02 to 5.0% of a water-insoluble mixture of approximately equal partsby weight of a primary alkyl amine having from 16 to 18 carbon atoms andan oil-soluble alkyl phenol.

2. A lubricating oil composition for the lubrication of steam turbinescomprising a major proportion of a hydrocarbon lubricating oil and from0.02 to 5.0% of a water-insoluble mixture of approximately equal partsby weight of octadecyl amine and 2,4-diamyl phenol.

3. A hydrocarbon oil composition for the lubrication of steam turbinescontaining a major proportion of a hydrocarbon oil and a minorproportion of a water insoluble, approximately equimolecular mixture ofan alkyl amine having from 16-18 carbon atoms and an oil-soluble alkylphenol.

4. A lubricating oil composition for the lubrication of steam turbinescomprising a major proportion of a hydrocarbon lubricating oil and from0.02 to 5.0% of a water-insoluble, approximately equi-moiecular mixtureof a primary alkyl amine having from 16-18 carbon atoms and anoil-soluble alkyl phenol.

ELMER W. COOK. WILLIAM D. THOMAS, JR.

